The invention relates to a guide vane system for a turbomachine in accordance with the present invention. The invention further relates to a turbomachine and to a method for assembling a guide vane system for a turbomachine.
Known from EP 2 884 055 A1 is a guide wheel for a turbomachine, for which guide vanes that are arranged in succession in the peripheral direction of the guide wheel and can be variably adjusted around their radially directed longitudinal axis are provided. An inner ring is arranged radially inward of the guide vanes. The guide vanes are mounted at their radially inner ends in respective recesses of the inner ring. In this case, at least one of the guide vanes has a sliding surface that is formed essentially perpendicular to the longitudinal axis and is arranged radially inward. The sliding surface and the inner ring form a frictional pairing. In this way, respective leakage at the bearing of the guide vane at the inner ring is especially reduced.
In this case, in order to secure the bearing of the guide vane at the inner ring, a securing pin, which is arranged in a plane perpendicular to the longitudinal axis of the guide vane, is joined to the radially inner end of the guide vane in a form-fitting manner. The variability of the guide vane and, in particular, its ability to twist around the longitudinal axis of the guide vane, is made possible in this case by means of a groove in the inner ring formed in the peripheral direction, in which the securing pin is guided. Each guide vane in this case is secured using a securing pin that is respectively associated with it. Alternatively, it is provided that the guide vanes are to be joined at their radially inner end in a form-fitting manner in the radial direction by means of a rivet connection or screw connection, which is arranged perpendicular to the longitudinal axis of the guide vane. Furthermore, there exists the possibility that a screw, which is arranged parallel to the longitudinal axis of the guide vane, is designed for fixing the inner ring in place at the radially inner-lying end of the guide vane. In these cases, too, a securing in the form of a rivet connection or a screw connection is provided for each guide vane. However, a drawback of the known securing systems is that, in this way, additional leakage pathways can be opened up in the axial direction, as a result of which the performance of the turbomachine is reduced.